||As the most well-known nanomaterial, poly(N-isopropylacrylamide) (PNIPAM) microgel is a thermo-responsive synthetic polymer, when heated in water above 32℃, it undergoes a reversible lower critical solution temperature phase transition. Thus, PNIPAM microgel has found numerous biomedical applications, such as drug delivery, biosensing, and so on. Cysteine is biologically essential protein for maintaining the appropriate redox status of cells, and organisms. Deficiency of cysteine is involved in slowed growth rate, edema, liver damage and weakness. Because cysteine level is associated with many disease, research for the selective detection of cysteine is intense interest and crucial. In this study, we synthesized fluorescent compound that have aldehyde functional groups to give selectivity toward thiol group of cysteine. The synthesized fluorescent compound is immobilized in PNIPAM to be applied in cysteine-responsive probe.